The perfect browser to me has several elements:
– renders web pages and applications as meant by the author
– gives authors/developers the ability to create rich web pages/content/applications
– allows users to interact with the web site in a complementary way (doesn't get in the way)
– puts the user in control of the experience (meaning extensible, customizable via options)
– has to be simple and efficient (meaning has to be familiar, easy to use, fast)